Local agencies and state governments are continually in need of drug abuse prevalence estimates for planning and resource allocation. Several mathematical models exist, such as multiple recapture censuses and synthetic estimator methods. These models are out of reach for everyday use by health planners, but can be adapted for use with "state-of-the- art" microcomputing (PCs) devices and software. Applied Sciences Research (ASR) proposes to identify and adapt methodologies from the mathematical sciences for estimating drug abuse prevalence; and, to develop software templates to be used on microcomputers (PCs) for the estimating procedures. During Phase I, ASR studied the feasibility for estimating the number of individuals who inject illicit substances subcutaneously (especially, heroine, cocaine, and amphetamines) and other multiple drug use. these drugs are being studied due to their high prevalence and their harmful physiological, social, and personal consequences. Most important, these drugs are often used by injection, putting the users at high risk for HIV infection and other blood-borne diseases. During Phase II, ASR proposes to develop detailed documentation and "cookbook" user manuals and microcomputer (PC) software as a marketable product. Applied Sciences Research successfully used small manageable data sets in Phase I in order to test and validate the procedures before proposing full development of the software and adaptation to larger data sets in Phase II, such as Standard Metropolitan Statistical Areas (SMSAs), large-sized counties or states.